1. Field of the Invention
The present invention relates to a master cylinder for a hydraulic brake or clutch release system of an automotive vehicle, and, more particularly, to a master cylinder including a cylinder body made of resin material which is molded and a piston which is slidably received within an inner cylinder surface of the cylinder body.
2. Description of the Prior Art
In the technical field relating to a brake master cylinder or the like for an automotive vehicle, a cylinder body has often been formed from a mold resin material in recent years to reduce the weight thereof.
Such master cylinder which is shown in FIG. 3 has a cylinder body 1 of resin material having at a rearward outer surface thereof two outward extending flanges 2 which are secured to a dash board of a vehicle body. A piston 4 which is slidably received within the cylinder body 1 is movable to the left by a push rod 3 in response to a depressing force on a brake or clutch release pedal. Therefore, the load in the left direction is applied on the cylinder 1 when the pedal is depressed and thus the outward extending flanges 2 may be deflected. This results in an increase of an idle stroke of the pedal.
In such master cylinder, the portions of the flanges 2 which are combined with the cylinder 1 are extremely thick in comparison with other portions of the cylinder 1. Therefore, the above combined portions will be contracted when molded and it is difficult to secure a true rounding of the inner surface of the cylinder 1. As a result, the inner surface of the cylinder 1 which corresponds to the above combined portions may not be applicable as a receiving portion within which the piston 4 is sealingly slidable. In order to secure the receiving portion by the desired length, the cylinder 1 has to be lengthened. It is noted that the inner surface of the cylinder 1 within which the piston 4 is directly received may not be processed to reduce the cost.